Elastic fluid turbine



Aug. 25, 1931. R. w. BAILEY ELASTIC FLUID TURBINE Filed Dec. 15, 1927 2 Sheets-Sheet l INVENTOR R.W.Bailey mm .M

WITNESS (3 ATTORNEY R. w. BAILEY 1,820,725

ELASTIC FLUID TURBINE Filed Dec. 15, 1927 2 Sheets-Sheet 2 Aug. 25, 1931.

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INVENTQR R.W-Bo||e ATTORNEY WITNESS Patented Aug. 25, 1931 UNITED STATES PATENT OFFICE RICHARD WILLIAM BAILEY, OF ALTRINCHAM, ENGLAND, ASSIGNOR, BY MESNE AS- SIGNMENTS, TO ASSOCIATED ELECTRICAL INDUSTRIES, LTD., OF ENGLAND ELASTIC FLUID TURBINE Application filed December 15, 1927, Serial No. 240,240, and in Great Britain December 17, 1926.

The invention relates to improvements in elastic fluid turbines, its main object being to overcome difiiculties attendant upon the use of high temperature motive fluids and 6 to enable turbines to be driven by motive fluid at substantially higher temperatures than has heretofore generally been possible in practice.

With most metals'commonly used in turbine construction, the mechanical strength diminishes as the temperature increases, for example, in the case of mild steel the strength falls rapidly as the temperature increases beyond 400" (1., so that definite limits of temperature are imposed, above which parts subjected to appreciable stresses must not be heated. This results in a limitation of the temperature of the motive fluid employed, so that in present turbine practice the maximum steam temperature is seldom greater than 400 0., while the development of the gas turbine is impeded by like con siderations.

' The invention provides a method of cool- 'ing elastic fluid turbines which consists in employing motive fluid as a cooling medium between parts at high temperature and highly stressed parts which it is desired to maintain at a lower temperature. Thus, zones of relatively cool motive fluid are interposed between zones of high temperature motive fluid and those machine parts which are subjected to appreciable stresses, said parts being thereby screened so that their temperatures may be constantly maintained below that of the high temperature motive fluid.

The whole or part of the motive fluid driving the turbine may provide the cooling medium, being taken after either its partial or complete expansion in the working stages of the turbine, V ing parts of the turbine from the heat of the motive fluid at higher temperatures, and also for cooling, to some extent, the parts subjected to the higher temperatures.

Two 01' more turbines or two or more different motive fluids or sources of motive fluid may be employed with advantage in carrying out the invention. The motive fluid of one and utilized for screen turbine e. g. a steam-driven turbine, may be employed as the cooling medium in another turbine'e. g. a gas-driven turbine, or in the same turbine there may be two or more sources of supply of motive fluid, the screening of the highly stressed parts from the heat of motive fluid from one source being advantageously efl'ected by motive fluid from another source. In such cases motive fluid may also be used for cooling before or at the same time as it performs work upon the turbine blades for example by the use of multi-tier blading, and furthermore the motive fluid from one source may subsequently mix with that from another source.

The invention will be more particularly advantageousfor use in cooling turbine rotors, for the stators can generally be readily cooled or strengthened to withstand the stresses imposed thereon, whereas the rotors are less accessible and are subjected to high centrifugal stresses against which it is diflicult to strengthen the rotor.

The arrangement generally preferred in both disc and cyhnder types of rotors, is the provision or an annular cooling zone of motive fluid screening the central portions of the rotors from the high temperature motive fluid passing through the blading portions. Such annular cooling zones may be aflordcd by the provision of longitudinal ducts formed in the body of the rotor for the passage of the cooling motive fluid therethrough or, for eX- ample, by the employment of multi-tier'bla-ding, to different tiers of which is supplied motive fluid at different temperatures, the ooler fluid thus providing an annular cooling zone with respect to the hotter fluid.

These and further features of the invention. are herein after more fully described with reference to the accompanying drawings 3., 2 and 3 show, more or less diatically in longitudinal section, conuons of turbines according to the inis a cross section of the rotor body of t.

turbine shown in Fig. 1; F 1g. 5 shows a detail in section and to an enlarged scale;

Fig. 6 shows in section a portion of multitier blading employed in one construction according to the invention;

Fig. 7 is a detailed cross sectional view of one form of rotor cooling duct;

Figs. 8 and 9 are, respectively, a sectiQnal elevation and plan of a turbine blade employed in carrying out the invention;

Fig. 10 is a view in the direction of the rotor axis showing a portion of a rotor and blading according to one construction for carrying out the invention; and,

Fig. 11 is a section corresponding to line XI-XI of Fig. 10.

In the'construction shown in Fig. 1 the rotor drum 1 is perforated by a plurality of longitudinal ducts 2 arranged to provide an annular cooling zone within the rotor drum, as indicated in Fig. 4. The annular cooling zone divides the rotor into and is disposed between a central portion 61 and an outer ortion 62 surrounding the central portion. fhe ducts 2 are spaced to provide portions 63 between adjacent ducts for connecting the central and outer portions and for transmitting centrifugal forces from the outer portion 62 and the blading carried thereby to the central portion 61, the central portion'being thereby subjected to radial tension stresses in resisting said centrifugal forces.

The motive gas or vapor at high temperature and pressure enters the cylinder 3 by the inlet 4 and performs work while flowing through the blading portion 5 as is usual. Upon leaving the blading portion 5 the gas or vapor, which has suffered a considerable drop in pressure and temperature in passing through the blading, is reversed in direction by the end wall 6 of the cylinder 3, and flows back through the ducts 2 within the rotor. Guide vanes 7 serve to minimize shock and energy losses upon reversal of the direction of the motive fluid and vanes 8 are also provided for a similar purpose at the end of the rotor where the cooling fluid leaves the ducts 2 and enters the exhaust chamber 9. A labyrinth gland 10 separates the inlet and exhaust chambers of the turbine.

The relatively cool motive fluid, in flowing through the ducts 2, takes up heat imparted by the hot motive fluid to the blades and adjacent portions of the rotor and conducted within the body of the rotor, particularly near the high pressure portions of the turbine. The central portion of the rotor adjacentthe axis thereof, which is, in operation, subjected to high stress, in resisting the centrifugal forces of the outer portion surrounding the same, is thus maintained at a temperature not greatly in excess of the temperature of the motive fluid leaving the bladadjacent portions of the rotor to which the blades are attached.

This form of my invention is particularl adapted for the use of steam as motive fluir which is exhausted through the chamber 9 preferably in partly expanded condition. My invention thus provides a reheater for the steam flowing through the turbine.

The heat taken up by the motive fluid may be utilized in any way that is convenient in the particular plant in question. An example wherein such heat may be usefully transformed into work in the same turbine, however, is illustrated in Fig. 2. In this example the turbine rotor comprises a portion 11 of cylindrical or drum form adapted to be driven by gaseous motive fluid, and two steam-driven portions 12, 13 of the disc type. Gas at high temperature and pressure is sup plied through the gas inlet 14, gives up energy 'in passing through the blading of the rotor portion 11, and leaves at a substantially lower temperature and pressure by the exhaust passage 15. High pressure steam is supplied to the inlet chamber 16 of the steam-driven portion 12 and after giving up some of its energy in performing work therein passes through ducts 17 in the rotor portion 11 where it serves as a cooling medium with respect to the high temperature gaseous motive fluid and is then delivered to the steam-driven portion 13. The portion 11 of the rotor is thus cooled, the heat energy taken up by the steam being expended in doing Work in the steam-driven portion 13 before the steam finally leaves by the exhaust passagelS.

The heat remaining in the gaseous motive fluid exhausted from the turbine'may be utilized, for example, as shown diagrammatically, for superheating the steam supplied to the turbine by a supply conduit 19, for heating the steam between two operative stages of the turbine portion13 by means of an inter stage re-heating circuit 20'and for heating the water from which the steam is generated by the provision of a further heating circuit as indicated at 21.

A further example wherein provision is made for supplying cooling motive fluid to the rotor independently of the motive fluid serving to drive same, is shown in Fig. 3. A reac ion turbine is shown having a rotor drum 22 formed with cooling ducts 23 similar to those shown in Fig. 1. The turbine is operated by gas at high temperature which is supplied to the inlet chamber 24 and leaves by the exhaust chamber 25 after performing work in passing through the blading portion 26. In order to balance the rotor the balancing piston 27 is mounted thereon, one side of the piston being subjected to the pressure of the gas in the inlet chamber 24 and the other side being subjected to the pressure of the exhaust gas communicated thereto by means of a pressure equalizing pipe 28 connecting the exhaust chamber with a .bal-

ancing pressure chamber 29.

Glands 31 are provided between the rotor and the cylinder, said glands respectively 6 separating the gas chambers 29, 25 from annular chambers 32, 33 adjacent the ends of the cylinder and through which the cooling motive fluid is supplied and drawn ofi, respectively. A further gland 34 is provided between the balancing piston 27 and the cylinder in order to limit the leakage of gaseous motive fluid from the chamber 24 to the chamber 29. Other glands 35, 36 are provided between the rotor and the cylinder at the ends of the latter in order to prevent communication between chambers 32, 33 and the external atmosphere. Passages 37 are provided withinthe piston 27 to afford communication be tween the chamber 32 and the ducts 23, and similarly a sleeve member 38 mounted on the rotor at the other end provides passages 39 between said ducts and the annular chamber As will be readily observed, cooling fluid, for example, high pressure steam, supplied to the chamber 32, flows through the passages 37 to the ducts 23 and then through passages 39 to the chamber 33 from which it is removed for use in a prime mover. In pass- 80 ing through the rotor such steam takes up heat transmitted from the gaseous motive fluid, thus cooling the rotor and leaving the chamber 33 in a superheated condition.

The pressure of steam in the chamber 32 or 33 is preferably greater than that of the gas in the adjacent chambers 29, 25, but if this is not the case, which might result in an undesired leakage of the gas into the steam system, the glands 30, 31 preferably comprise, as shown in greater detail in Fig. 5, an annular recess 40 enclosed on both sides by labyrinth packing 41 of any suitableform. Steam at higher pressure thanthegas in the adjacent gas chamber 29 or 25, as the case maybe, is supplied through the cylinder to the annular recess 40 so that leakage can only take place by the passage of high. pressure steam into the adjacent gas or steam chambers, and in no event can the gas enter the cooling system so as to deleteriously affeet the steam for use as motive fluid.

A similar form of gland may be employed between the steam-driven portion 12 and the gas-driven portion 11 and if desired also-between the latter and the steam-driven portion 13 of the turbine described above with reference to Fig. 2.

Motive fluid from two different sources may also be employed in a turbine so that the motive fluid from one source serves as cooling medium with respect to the motive fluid from the other source at the same time as it performs work upon the turbine blading. An example of such a case is illustrated in Fig. 6 which shows a portion of double-tier blading,

to the outer tier 42 of which high temperature motive fluid is supplied, while the inner tier 43 is supplied with motive fluid that is at a substantially lower temperature. The pressures of the motive fluids at high and low temperatures respectively may be approximately the same, but preferably that of the low temperature motive fluidis the greater so that there is no possibility of the hotter fluid flowing towards the axis of the rotor. Any tendency for the two motive fluids to mix may, if desired, be minimized by the provision of labyrinth packing 44 mounted on the partitions 45 between the tiers.

In turbines of this construction it may in some cases be advantageous to permit the two motive fluids to mix in the blading portions towards the low pressure end of the turbine, where thetemperature of'the motive fluid flowing in the outer tier is no longer excessive, the double-tier blading as and for the purpose above described being employed es sentially at the high pressure end of the turbine. Naturally, however, the multi-tier blading construction may also be carried completely to the exhaust if desired.

This method of construction whereby an annular cooling zone is'provided to protect the interior region of the rotor from the effects of high temperature motive fluid may also be carried out with blading comprising more than two tiers. For example, by the use of three-tier blading in which high temperature motive fluid is supplied to the central tier and cooler motive fluid to the inner and outer tiers, some measure of protection for the cylinder as well as for the rotor may be afforded.

In applying the invention in practice, various further constructional details may be employed to hinder the conduction of heat from the blades and portions of the turbine in direct contact with the high temperature motive fluid and to facilitate the delivery of heat to the cooling medium. Thus, the cooling ducts or passages in the rotor may be provided with internal ribs 45' (Fig. 7) carried by tubular members 46 preferably of a metal of high thermal conductivity inserted into longitudinal bores in the rotor so as to make good thermal contact with the walls of said bores. Alternatively, the ribs may be formed integrally with the rotor.

Moreover in blading constructions in which the root portions of the blades are enlarged and thereby ofler considerable surfaces for contact with the high temperature-motive fluid, a gap 47 of suitable dimensions may be provided in the root portion 48 of the blade as shown in Figs. 8 and 9,'so that the conduction of heat across the root is interrupted and the flow of heat towards the axis of the rotor thereby reduced. For similar purposes, in the multi-tier blading constructions above mentioned, the partitions be able manner.

tween the tiers may be slotted. Furthermore, heat insulating material may also be interposed between the various machine parts as will be apparent.

An improved construction of rotor and blading which may be employed with advantage in carrying out the invention is illus trated inFigs. l0 and 11. The cooling ducts in the rotor are formed by longitudinal slots 49 adjacent the periphery thereof, the outer portions of said slots being dovetailed for the purpose of holding segments of blades 50, inserted with their correspondingly dovetailed projections 51 into the ends of the slots 49 and moved longitudinally into the desired position on the rotor. The blading segments thus serve to cover the slots on the outside and thereby provide the closed rotor cooling ducts. The blading segments may be formed with slots 52 for the purpose of interrupting the conduction of heat towards the centre of the rotor.

Any numberof blades may be carried by one segment, which may extend axially over more than one ring of blades and over any number of slots and if desired, spacing rings or segments may be provided between the blade rings to ensure the proper separation ofthe latter and assist in covering the slots of the rotor. The ends of adjacent segment pieces are preferably tongued and grooved or half-lapped to permit freedom of expansion circumferentially while preventing leakage of steam therebetween in an axial direction.

In applying the invention to the cooling of the stator or cylinder, ducts may be formed therein as above described with reference to the rotor, or the casing may be otherwise provided with jackets through which the cooling motive fluid is passed in any suit- It should also be noted that the invention may be employed in conjunction with other cooling systems. That is to say, the cooling fluid may be employed where appropriate to take up heat in other known cooling systems before or after serving as a cooling medium in the turbine as above described. or other known cooling systems for a turbine may be employed in addition to the'measures above described, for example, by the supply of cooling-air or water through the central bore 53 of the rotor as indicated in Figs. 1, 3 and 4.

It will readily be appreciated that by the invention above set forth, motive fluid at considerably higher temperatures than has hitherto been practicable may be employed, those parts which are directly exposed to the motive fluid at its highest temperature may be formed of special heat-resisting steels or other metals or alloys, while other portions are screened and their temperatures maintained within suitable limits according to their character and the nature of the stresses imposed upon them.

While I have shown my invention in sev- I eral forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is 1. An elastic fluid turbine including a casing and a rotor having cooperating blading portions, said rotor having longitudinal ducts in the body thereof arranged to form a substantially annular cooling zone between the blading portion and the center portion of the rotor body, and means for conveying motive fluid discharged from said blading portion of said ducts.

2. An elastic fluid turbine including a casing and a rotor having cooperating blading portions, said rotor having longitudinal ducts extending therethrough, and guide its means for directing motive fluid discharged from a stage of said blading to said. ducts for cooling the rotor.

3. An elastic fluid turbine according to claim 2. who-rein said guide vanes serve to reverse the direction of flow of the motive fluid so that in passing through the rotor ducts it serves to coolparts of the rotor which were previously heated by said motive fluid when performing work upon the blades of said rotor.

4. An elastic fluid turbine wherein a turbine rotor portion adapted to utilize the energy of motive fluid at high temperature is formed with cooling ducts through which motive fluid at lower temperature and in partly expanded condition flows in passing from an operative turbine stage.

5. In a high temperature elastic fluid turbine, a casing, a rotor, cooperating blading portions carried by said casing and rotor and adapted to partially expand the motive fluid flowing therethrough. a passage extending longitudinally through said rotor, and means for conveying said partially expanded motive fluid through said passage for cooling said rotor.

In testimony whereof, I have hereunto subscribed my name this 24th day of November,

RICHARD WILLIAM BAILEY. 

